Up until the last few years, the noise analysis algorithms used
for RF circuits were so computationally expensive that only circuits
with a few dozen transistors could be analyzed in a reasonable
period of time. The recent development of matrix-implicit iterative
methods, and their use in eigen analysis approaches, has changed
this dramatically, and now noise analysis of circuits with thousands
of transistors is routine. These faster methods have been applied
to both spectral and time-domain analysis techniques, and in this
talk we will try to drawn commonalities between the two methods
and discuss several approaches to noise analysis.